[PATCH 1/8] x86, mce: stop calling del_timer_sync() from interrupt

Hidetoshi Seto
2011-06-17T08:41:15Z

Function del_timer_sync() has WARN_ON(in_irq()) in it because
calling it from interrupt context can cause deadlock if it
interrupts the target timer running.

In MCE code, del_timer_sync() is used with on_each_cpu() in
some parts for sysfs files:
bank*, check_interval, cmci_disabled and ignore_ce.

However use of on_each_cpu() results in calling the function
passed as the argument in the interrupt context. It means you
can see a flood of warnings from del_timer_sync() by a simple
file access, for example:

echo 300 > /sys/devices/system/machinecheck/machinecheck0/check_interval

Fortunately these MCE specific files are rare-used and AFAIK
only few MCE geeks experience this warning on write.

To remove the warning (for my happy hacking), move timer deletion
outside of the interrupt context ;-)

v2: update patch description

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
---
arch/x86/kernel/cpu/mcheck/mce.c | 22 ++++++++++++++++------
1 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 08363b0..42fc8d2 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1140,6 +1140,17 @@ static void mce_start_timer(unsigned long data)
add_timer_on(t, smp_processor_id());
}

+/* Must not be called from interrupt where del_timer_sync() can deadlock */
+static void mce_timer_delete_all(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ if (mce_available(&per_cpu(cpu_info, cpu)))
+ del_timer_sync(&per_cpu(mce_timer, cpu));
+ }
+}
+
static void mce_do_trigger(struct work_struct *work)
{
call_usermodehelper(mce_helper, mce_helper_argv, NULL, UMH_NO_WAIT);
@@ -1750,7 +1761,6 @@ static struct syscore_ops mce_syscore_ops = {

static void mce_cpu_restart(void *data)
{
- del_timer_sync(&__get_cpu_var(mce_timer));
if (!mce_available(__this_cpu_ptr(&cpu_info)))
return;
__mcheck_cpu_init_generic();
@@ -1760,16 +1770,15 @@ static void mce_cpu_restart(void *data)
/* Reinit MCEs after user configuration changes */
static void mce_restart(void)
{
+ mce_timer_delete_all();
on_each_cpu(mce_cpu_restart, NULL, 1);
}

/* Toggle features for corrected errors */
-static void mce_disable_ce(void *all)
+static void mce_disable_cmci(void *data)
{
if (!mce_available(__this_cpu_ptr(&cpu_info)))
return;
- if (all)
- del_timer_sync(&__get_cpu_var(mce_timer));
cmci_clear();
}

@@ -1852,7 +1861,8 @@ static ssize_t set_ignore_ce(struct sys_device *s,
if (mce_ignore_ce ^ !!new) {
if (new) {
/* disable ce features */
- on_each_cpu(mce_disable_ce, (void *)1, 1);
+ mce_timer_delete_all();
+ on_each_cpu(mce_disable_cmci, NULL, 1);
mce_ignore_ce = 1;
} else {
/* enable ce features */
@@ -1875,7 +1885,7 @@ static ssize_t set_cmci_disabled(struct sys_device *s,
if (mce_cmci_disabled ^ !!new) {
if (new) {
/* disable cmci */
- on_each_cpu(mce_disable_ce, NULL, 1);
+ on_each_cpu(mce_disable_cmci, NULL, 1);
mce_cmci_disabled = 1;
} else {
/* enable cmci */
--
1.7.1